Gale Watch 15, NWS Los Angeles, CA

Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
1032 PM PDT Wed Apr 7 2021

updated aviation discussion

.SYNOPSIS...07/749 PM.

Gusty northwest to north winds will affect southern Santa Barbara
County and northern Los Angeles County through late Saturday.
There will be patches of night through morning low clouds and fog
in some coastal and valley areas through this week. Temperatures
will be 5 to 10 degrees above normal in most areas. Much cooler
conditions are expected for the first half of next week with
expanding low clouds and fog.

&&

.SHORT TERM (WED-SAT)...07/854 PM.

***UPDATE***

Except for some passing high clouds from the west, skies are
mostly clear across the area. Low clouds and fog are expected to
form over portions of the Central Coast and Salinas Valley after
midnight, but wouldn't be surprised if they did not form due to
the upper ridge remaining overhead along with gusty northerly
flow. Models indicate a weak eddy forming early Thursday and low
clouds may follow suit across the southern LA County coast, but
again the northerly flow may win out keeping it clear.

The main story tonight through the short term is wind. The gusty
winds across the Antelope Valley earlier today are on the decline
but still remain breezy. Along with reduced mountain wave
activity, have decided to cancel the Wind Advisory. Will update
the forecast accordingly. Gusty northerly winds continue across
southern Santa Barbara County, especially the western portion
where Gaviota is currently gusting to 53 mph. No surprise with a
SBA-SMX gradient of -5.2 mb! Other wind-prone areas are gusting
more along the lines of 35 to 45 mph. These winds will continue
overnight, and likely weaken a bit by Thursday morning. Local
gusts to 55 mph are possible through the passes and canyons of the
western portion through the overnight hours.

Thursday still looks on track for widespread gusty northerly
winds, including for southern Santa Barbara County, the I-5
corridor, Santa Clarita Valley, and possibly the San Fernando
Valley, peaking Thursday night and Friday. Temperatures across the
coastal and valley sections should see a couple degrees of warming
while the interior will cool by 5 to 8 degrees, but remain 5 to 10
degrees above normal.

***From Previous Discussion***

Left the High Wind Watches unchanged for Santa Barbara County.
Very confident that it will be windy, but with the weaker pressure
gradients it is now teetering between a strong Advisory and a
weak Warning. Will wait for some more guidance to decide how to
deal with it. Still expecting winds to impact the Santa Clarita
Valley, San Fernando Valley, eastern Ventura Valleys, and Santa
Monica Mountains Thursday and Friday. Gusts should peak there
between 30 and 40 mph. The Santa Clarita valley should see
Advisory level winds, and while those other areas may also need
one, they look unlikely at this point. All of these winds will
create travel hazards, as well as the potential for power outages
and issues to portable structures.

The Central Coast and Salinas Valley should still see some low
clouds each morning. Other areas should stay clear except for a
chance of some clouds over southeast LA County each morning. With
the increasing winds, coastal and valley areas should see some
additional warming tomorrow with little change through Saturday.

.LONG TERM (SUN-WED)...07/228 PM.

Models and ensembles are in better agreement for early next week.
The upper level ridge from this week, will quickly move off the
coast Sunday and Monday as a series of pass troughs the northern
Rockies. Some projections show one of these troughs digging down
somewhere between California and Utah late Tuesday and Wednesday.
All of this should result in cooling for the first half of next
week, and a substantial marine layer expansion. With the
increasing onshore flow, interior areas should see gusty west
winds as well.

&&

.AVIATION...08/0530Z.

At 0430Z at KLAX, the marine layer was 800 feet deep. The top of
the inversion was at 1800 feet with a temperature of 20 degrees
C.

Moderate confidence in KSMX, KPRB, and KSBP where there is a 30%
chance of no cigs. If cigs do form, timing of arrival may be off
by +/- an hour. Moderate to high confidence in KLAX, KLGB, and
KSMO where there is a 20-30% chance of IFR to LIFR cigs after 09Z,
with the higher confidence for KLGB. Otherwise high confidence in
remainder of TAFs.

KLAX...Moderate to high confidence in the 06Z TAF. There is a
20-30% chance of IFR or LIFR cigs after 10Z. High confidence that
any east wind component will be 5 kt or less.

KBUR...High confidence in the 06Z TAF.

&&

.MARINE...07/739 PM.

Moderate to high confidence in Gale force gusts continuing through
late tonight for the waters from Point Conception to San Nicolas
Island. Winds have been gusting around 30 kt early this evening,
but may strengthen later this evening. For the waters along the
Central Coast, high confidence in Small Craft Advisory (SCA) level
winds continuing through late tonight. There is a 40% chance of
Gale force gusts for the outermost portion of these waters. High
confidence in SCA level winds across all these waters late tonight
through Thursday morning.

By Thursday afternoon, high confidence in at least SCA level winds
across all the waters. This includes the Santa Barbara Channel and
waters adjacent to LA and Orange Counties, but mainly for the
western portions. Once again there is moderate to high confidence
in Gale force gusts across the waters from Point Conception to San
Nicolas Island by Thursday afternoon or early evening. Winds will
diminish some during the overnight hours, then Friday will be much
of the same. Another round of Gales are likely, this time
extending northward to the outermost waters along the Central
Coast. Similar conditions will continue through Saturday night
before winds finally settle down on Sunday.

These gusty winds will produce steep, short-period wind waves
across all the waters which will be hazardous to mariners.

&&

.FIRE WEATHER...07/157 PM.

Dry weather can be expected through the rest of the week and
likely into the weekend.  Minimum humidities across the
interior areas and mountains will lower into single digits to
lower teens both Thursday and Friday, with generally poor
overnight recoveries.

A good northerly surface pressure gradient pattern will
result in gusty northwest to north canyon winds during the
overnight and morning hours across central and western portions
of the Santa Barbara County south coast, strongest from
Thursday night into Saturday morning, when gusts up to 40-60
mph will be possible at times. Gusty west to northwest winds up
to 50 mph at times will affect the mountains of Los Angeles
County and the Antelope Valley through Friday, strongest each
afternoon and evening. Finally, gusty mainly north winds up
to 40 mph can be expected at times Thursday and Friday for
the Santa Clarita Valley, San Fernando Valley and Santa Monica
Mountains.

The combination of gusty winds and low humidities will bring
elevated fire weather conditions to interior areas including the
mountains and deserts for Thursday and Friday. There could also
be a few hours of critical fire weather conditions each day in
these areas, but due to the relatively high moisture content in
the live fuels, Red Flag Warnings are NOT expected to be issued
for this event.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory in effect until 6 PM PDT Thursday for zones
      39-52. (See LAXNPWLOX).
     High Wind Watch in effect from Thursday evening through
      Saturday morning for zones 39-52. (See LAXNPWLOX).
     Wind Advisory in effect until 3 AM PDT Friday for zones
      53-54. (See LAXNPWLOX).
     Wind Advisory in effect from noon Thursday to 3 AM PDT Friday
      for zone 88. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 2 AM PDT Thursday for
      zone 645. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Friday for
      zones 650-655. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 PM PDT Friday for zone
      670. (See LAXMWWLOX).
     Gale Watch in effect from Friday afternoon through late
      Saturday night for zone 670. (See LAXMWWLOX).
     Gale Warning in effect until 3 AM PDT Thursday for zones
      673-676. (See LAXMWWLOX).
     Gale Watch in effect from Thursday afternoon through late
      Saturday night for zones 673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (SAT-WED).

Gusty north winds will continue through late Saturday, focused
over Santa Barbara County and Los Angeles County, including some
valleys and coasts as well as the coastal waters. Expect hazardous
driving and boating conditions, downed trees and power outages,
as well as damage to portable shelters. Gusty west winds possible
over interior areas early to middle of next week.

&&

PUBLIC...Stewart/Kittell
AVIATION...Stewart/Smith
MARINE...Stewart
FIRE...Sirard
SYNOPSIS...RK/Smith

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